Microbiology of cerebral abscess: a four-year study in Malaysia

A prospective study was carried out to determine the aetiology of cerebral abscess in relation to the primary source of infections. Seventy-five patients with cerebral abscess were included in the study in the period January 1985 to December 1988. More than half of the patients studied had single lesions and the overall most common sites were in the frontal and parietal regions. Chronic suppurative otitis media, cyanotic congenital heart diseases and meningitis were among the important predisposing conditions in these patients. Approximately 25% of the patients with cerebral abscesses had no documented antecedent infections. Pure cultures were found to be predominant (66.7%) and sterile cultures were obtained from 10 (13.3%) patients. Streptococci were isolated from 23 (30.7%) patients, the commonest species being Streptococcus milleri. Proteus sp, Pseudomonas aeruginosa, Pseudomonas putrifaciens and Bacteroides sp were almost exclusively found in cerebral abscesses secondary to chronic suppurative otitis media; these organisms were found in mixed cultures. Streptococcus milleri, Bacteroides sp and Eikenella corrodens were found in pure cultures in patients with cyanotic congenital heart disease. In patients with ventriculoperitoneal shunts in-situ, Staphylococcus aureus, Staphylococcus epidermidis and diphtheroids were common. Anaerobes were found in 15 (20.0%) patients, the majority in mixed cultures. Culture, as well as gas-liquid chromatographic analysis of volatile fatty acids of cerebral pus, was carried out to enhance the detection of the anaerobes. Based on these findings, an antibiotic regimen consisting of penicillin, chloramphenicol and metronidazole is recommended as an initial therapy while awaiting culture and sensitivity results.